Such seals are well known for example in the field of gas turbines. The seals are used for sealing between static components of a turbine respective at the interfaces of turbine components, for example for sealing cooling-air paths in guide blades, for sealing between the individual segments of a guide blade row or as a circumferential seal between a casing part of the turbine and a guide blade row or for sealing component interfaces between the combustor and the turbine.
This type of seal is described, for example, in U.S. Pat. No. 5,743,708 and is shown there in particular with respect to FIGS. 17 and 18. The seal there consists only of a single part, this is a flat metallic piece, which has a respective solid bulge on two opposite sides. As viewed in the cross section, the seal has a long narrow centre piece, which has a round bulge at each of its ends. On account of its cross-sectional shape, it is referred to as a “dog bone seal”. It is arranged there at the first guide blade row in each case between adjacent guide blade platforms and serves there to seal cooling-air paths for the purpose of cooling the outer and inner platforms of the guide blades.
The solid, round bulges are each arranged in a groove of adjacent guide blade platforms, in the course of which they bear tightly against the inner surfaces of the groove. The seals extend in each case over a side length of a platform. The seal is mainly brought about by a pressure difference, the seal being obtained along lines on the side surfaces of the groove, where the rounded bulges touch the flat insides of the grooves. In this case, the seal has to be ensured by the bulges in both grooves.
This typical conventional dog bone seal has a robust design, but unfortunately only a low flexibility to relative axial/radial movements of the turbine components. Furthermore, it has as additional disadvantages excessive wear in some occasions and degradation of sealing performance with aging (increased leakage to aging of the seal itself).
A variant of this dog bone seal type is disclosed in U.S. Pat. No. 5,868,398. It also serves here to seal between adjacent guide blade segments. However, the bulge at the sides of the seal is not of solid design, but rather is realized by a curvature of the flat metallic piece, the curved parts are set into a groove.
This seal has also the disadvantage that, in the event of an inadequate pressure difference, the bulges do not bear sufficiently tightly and leakage results. Furthermore, the seal is not fully ensured if one or both static parts of the turbine shift axially or radially and the grooves shift relative to each other, that means the seal is not flexible enough.
An improved seal between two static turbine parts is known from U.S. Pat. No. 6,431,825 B1. This seal does not depend on the level of a pressure differential. It is provided with a carrier piece comprising a flat metal piece with a middle piece and end pieces each of which is arranged in a groove in the static turbine parts. A second part comprising also a flat metal piece and having a middle piece and end pieces, which are also arranged in the grooves is attached to the middle piece of the carrier. The end pieces are constructed resiliently, ensuring a sealing contact between the end pieces and the inside surfaces of the grooves even in case of a relative shift off the grooves.
In addition, flexible seals for sealing between static turbine components of different types are known, for example membrane seals or cloth seals, but such seals are not are very robust.
Document EP 2 530 251 A2 describes a hinge seal to absorb different thermal growth of vessels. The hinge seal comprises a middle piano hinge portion which flexes, curves and/or flattens in case there is a relative translation between the vessels.
Document US 2005/0179215 A1 describes a a seal device in form of a “dog-bone” consisting of a plurality of seal strips fabricated from sheet material and connected via at least a connection rod or connection bar, which is inserted into through holes in the strips before the both rod ends are welded to the seal strips. This connection rod makes layers of seal strips to be joined at both ends in order to form a joint section.